Tissue removal device for neurosurgical and spinal surgery applications

ABSTRACT

A tissue cutting device that is especially suited for neurosurgical applications is disclosed and described. The device includes a handpiece and an outer cannula in which a reciprocating inner cannula is disposed. The inner cannula includes a hinge between a body section and a cutting section that allows the cutting section to pivot when the inner cannula reciprocates within the outer cannula. A tissue collector is also provided and is in fluid communication with the lumen of the inner cannula. The inner cannula reciprocates at a rate that is greater than 1000 reciprocations per minute, and variable aspiration may also be provided to the device to control tissue traction and provide fine shaving and debulking.

TECHNICAL FIELD

The present disclosure relates to tissue cutting devices, in particular, tissue cutting devices that are suited for neurosurgical and spinal surgical procedures.

BACKGROUND

Various abnormalities of the neurological system, such as brain and spinal tumors, cysts, lesions, or neural hematomas, can cause severe health risks to patients afflicted by them, including deterioration in motor skills, nausea or vomiting, memory or communication problems, behavioral changes, headaches, or seizures. In certain cases, resection of abnormal tissue masses is required. However, given the complexity and importance of the neurological system, such neurosurgical procedures are extremely delicate and must be executed with great precision and care. Many known tissue cutting devices suffer from an inability to quickly and cleanly sever neurological tissue samples without causing “traction” or pull on the surrounding tissue. In addition, many known devices are not configured to both “debulk” large structures and to finely shave smaller, more delicate structures and lack the flexibility needed in many procedures. Furthermore, many neurological procedures impose significant space limitations on the surgeon, and the tissue resection device needs to be manipulable by the surgeon with one hand in relatively small spaces. Many known devices either emulsify the resected tissue, macerate the resected tissue, or thermally damage the tissue rendering it unsuitable for subsequent analysis (e.g., pathologic and/or histologic analysis) which is necessary for the determination of the most effective post resection treatment therapies. Thus, a need has arisen for a tissue cutting device that addresses the foregoing issues.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described by way of example in greater detail with reference to the attached figures, in which:

FIG. 1 is a perspective view of a tissue cutting device in accordance with a first embodiment;

FIG. 2 is a cross-sectional view of the tissue cutting device of FIG. 1 depicting an inner cannula in a first relative position with respect to an outer cannula in which the inner cannula's distal end is located proximally of the outer cannula's distal end;

FIG. 3 is a cross-sectional view of the tissue cutting device of FIG. 1 depicting the inner cannula in a second relative position with respect to the outer cannula in which the inner cannula's distal end is located at the distal end of the outer cannula;

FIG. 4 is a partial cross-sectional view of the tissue cutting device of FIG. 1 in a first configuration in which a device-mounted tissue collector is disconnected from a tissue cutting device housing;

FIG. 5 is a partial cross-sectional view of the tissue cutting device of FIG. 4 in a second configuration in which the device-mounted tissue collector is connected to the tissue cutting device housing;

FIG. 6 is a partial cross-sectional view of an alternate embodiment of the tissue cutting device of FIG. 1 in a first configuration in which the device-mounted collector is disconnected from the tissue cutting device;

FIG. 7 is partial cross-sectional view of the tissue cutting device of FIG. 6 in a second configuration in which the device-mounted tissue collector is connected to the tissue cutting device;

FIG. 8 is a broken side elevation view of the outer cannula of the tissue cutting device of FIG. 1;

FIG. 9 is a broken side elevation view of the inner cannula of the tissue cutting device of FIG. 1;

FIG. 10 is a top plan view of a portion of the outer cannula of the tissue cutting device of FIG. 1 with the inner cannula removed from the outer cannula;

FIG. 11 is a top plan view of a portion of the inner cannula of the tissue cutting device of FIG. 1;

FIG. 12 is a top plan view of a portion of the outer cannula and inner cannula of FIG. 1 depicting the inner cannula inserted into the outer cannula;

FIG. 13 is a partial cross-sectional view of a distal region of the outer cannula and the inner cannula of the tissue cutting device of FIG. 1, depicting the inner cannula in a first relative position with respect to the outer cannula;

FIG. 14 is a partial cross-sectional view of a distal region of the outer cannula and the inner cannula of the tissue cutting device of FIG. 1, depicting the inner cannula in a second relative position with respect to the outer cannula;

FIG. 15 is an exploded assembly view of the tissue cutting device of FIG. 1;

FIG. 16 a is a side elevation view of a cam of the tissue cutting device of FIG. 1;

FIG. 16 b is an end elevation view of the cam of FIG. 16 a;

FIG. 17 a is a perspective view of a cam transfer mechanism of the tissue cutting device of FIG. 1;

FIG. 17 b is a perspective view of a cam follower of the tissue cutting device of FIG. 1;

FIG. 18 is a partial perspective view of a portion of the tissue cutting device of FIG. 1 with an upper shell of an outer sleeve upper housing removed to show a dial for rotating the outer cannula;

FIG. 19 is a partial side cross-sectional view of the portion of the tissue cutting device of FIG. 18;

FIG. 20 is a side elevation view of an inner and outer cannula assembly of the tissue cutting device of FIG. 1;

FIG. 21A is a tissue cutting system including a remote tissue collector, control console, foot pedal, and the tissue cutting device of FIG. 1;

FIG. 21B is an enlarged view of the remote tissue collector of FIG. 21A;

FIG. 22 is a block diagram of a control scheme for the tissue cutting system of FIG. 22;

FIG. 23 is diagram of the tissue cutting device of FIG. 1 and the motor control unit of FIG. 22;

FIG. 24 is a partial cross-sectional view of the tissue cutting device of FIG. 1 depicting motor shaft position sensors for controlling a stop position of an inner cannula;

FIG. 25 is a partial cross-sectional view of the outer cannula and inner cannula of the tissue cutting device of FIG. 1 with the inner cannula in a first position relative to the outer cannula;

FIG. 26 is a partial cross-sectional view of the outer cannula and inner cannula of the tissue cutting device of FIG. 1 with the inner cannula in a second position relative to the outer cannula; and

FIG. 27 is a partial cross-sectional view of the outer cannula and the inner cannula of the tissue cutting device of FIG. 1 with the inner cannula in a third position relative to the outer cannula.

DETAILED DESCRIPTION

Referring now to the discussion that follows and also to the drawings, illustrative approaches to the disclosed systems and methods are shown in detail. Although the drawings represent some possible approaches, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present disclosure. Further, the descriptions set forth herein are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description.

Described herein are tissue cutting devices that are suited for neurosurgical applications such as the removal of spine and brain tissue. The devices are configured to provide high speed reciprocation, variable aspiration, and/or combinations of both high speed reciprocation and variable aspiration. As a result, the tissue cutting devices of the present disclosure provide surgeons with an enhanced ability to vary and control the extent of tissue cutting as well as the impact on surrounding tissue during tissue cutting procedures.

Referring to FIG. 1, a tissue cutting device 40 includes a handpiece 42 and an outer cannula 44. In one exemplary configuration, handpiece 42 is generally cylindrical in shape and is preferably sized and shaped to be grasped with a single hand. Handpiece 42 includes a lower housing 50 which comprises a proximal section 46 and distal section 48. Lower housing 50 comprises a proximal-most housing portion 82 (FIGS. 2 and 3) that is connected to a motor housing 71, and a cam housing 69 that is connected to motor housing 71. A front housing section 51 is connected to cam housing 69. Upper housing 42 is also provided. A tissue collector 58 may be operatively connected to upper housing 52 (as will be explained in further detail below). A rotation dial 60 for rotating the outer cannula 44 with respect to handpiece 50 is also mounted to upper housing 52.

As best seen in FIGS. 2, 3, and 20, outer cannula 44 includes an open proximal end 45, a closed distal end 47, and a distal opening 49 proximate distal end 47. Tissue cutting device 40 further comprises an inner cannula 76 which is partially disposed in an outer cannula lumen 110. Inner cannula 76 is configured to reciprocate within outer cannula lumen 110 and to cut tissue samples entering outer cannula 44 via outer cannula distal opening 49, as will be described in greater detail below. Inner cannula 76 reciprocates between a proximal position, which is depicted in FIG. 2 and a distal position which is depicted in FIG. 3. Inner cannula 76 includes an open proximal end 77 and an open distal end 79. Distal end 79 is preferably configured to cut tissue, and in preferred embodiments is capable of cutting neurological system tissues such as those from the brain or spine. In one exemplary embodiment, inner cannula distal end 79 is beveled in a radially inward direction to create a sharp circular tip and facilitate tissue cutting.

Outer cannula 44 is not translatable, and its position with respect to handpiece 42 along the direction of the longitudinal axis of handpiece 42 remains fixed. Motor 62 is disposed in proximal lower housing section 46 of handpiece 42 and is operably connected to inner cannula 76 to drive the reciprocation of inner cannula 76 within outer cannula lumen 110. Motor 62 may be a reciprocating or rotary motor. In addition, it may be electric or hydraulic. However, in the embodiment of FIGS. 2 and 3, motor 62 is a rotary motor, the rotation of which causes inner cannula 76 to reciprocate within outer cannula lumen 110.

Motor 62 is housed in motor housing 71, which defines a portion of lower housing proximal section 46. Motor 62 is connected to an inner cannula drive assembly 63 which is used to convert the rotational motion of motor 62 into the translational motion of inner cannula 76. At its proximal end, motor housing 71 is connected to proximal-most housing portion 82, which includes a power cable port 84 and a hose connector 43, which in the exemplary embodiment of FIG. 3 is an eyelet. Hose connector 43 provides a means of securely retaining a vacuum system hose to handpiece 42, thereby allowing vacuum to be supplied to tissue collector 58.

Inner cannula driver assembly 63 (not separately shown in figures) comprises a cam 64, a cam follower 68, a cam transfer 72, and a cannula transfer 74. Cam 64 is a generally cylindrical structure and is shown in detail in FIGS. 16A and 16B. A groove or channel 65 is defined in the surface of cam 64. In one exemplary embodiment, groove 65 is continuous and circumscribes the perimeter of cam 64 but is not oriented perpendicularly to the longitudinal axis of cam 64, i.e., groove 65 is angled with respect to the cam axis. Opposing points on groove 65 such as points 65 a and 65 b define pairs of “apexes” that are spaced apart along the longitudinal axis of the cam, i.e., the groove extends along a portion of the length of the cam. Cam 64 also includes a proximal opening 114 (FIG. 16 a) for receiving a motor shaft and a proximal recess 116 into which a shaft may be snugly received. Holes 118 and 120 are provided for mounting position indicators that cooperate with a position sensor to determine the angular position of cam 64, and correspondingly, the linear position of inner cannula 76 within the outer cannula lumen 110, as discussed below.

Cam follower 68 is depicted in detail in FIG. 17B. Cam follower 68 is a generally rectangular block shaped structure with a hollow interior in which cam 64 is partially disposed. Cam follower 68 also includes a hole 70 in its upper face in which a ball bearing (not shown) is seated. The ball bearing rides in cam groove 65 and engages cam transfer 72. As a result, when cam 64 rotates, cam follower 68 translates along the length of handpiece 42. Cam follower 68 also includes lateral slots 182 a and 182 b that cooperatively engage corresponding members 178 a, 178 b from cam transfer 72.

Cam follower 68 is disposed within a cam chamber 67 formed in cam housing 69. Cam 64 is partially disposed in cam chamber 67 and extends proximally therefrom to engage motor 62. Cam housing 69 comprises part of distal portion 48 of handpiece 42. Cam 64 does not reciprocate within cam chamber 67 and instead merely rotates about its own longitudinal axis. However, cam follower 68 reciprocates within cam chamber 67 along the direction of the length of handpiece 42. Cam follower 68 is open at its proximal end to receive cam 64. As shown in FIGS. 15 and 16A, cam 64 may optionally include a threaded distal end 123 that projects through a distal opening 191 (FIG. 17 b) in cam follower 68 and which engages a nut 190 (FIG. 15) to prevent reciprocation of cam 64 relative to cam housing 69. Proximal cam bearing 186 and distal cam bearing 188 (FIG. 15) may also be provided to support cam 64 as it rotates within cam housing 69.

Cam transfer 72 extends from cam chamber 67 into a cam transfer chamber 73 formed in upper housing 52. As best seen in FIG. 17 a, cam transfer 72 comprises a proximal end 72 a that is attachable to cam follower 68 and a distal end 72 b that is attachable to inner cannula 76 via cannula transfer 74. Proximal end 72 a comprises a pair of spaced apart, downwardly extending members 178 a and 178 b, and distal end 72 b comprises a pair of spaced apart upwardly extending members 180 a and 180 b. Downwardly extending members 178 a and 178 b are spaced apart in a direction that is perpendicular to the length of cam 64 and handpiece 42, while upwardly extending members 180 a and 180 b are spaced apart in a direction that is parallel to the length of cam 64 and handpiece 42. Cam follower slots 182 a and 182 b engage downwardly extending members 178 a and 178 b of cam transfer 72. Downwardly extending members 178 a and 178 b of cam transfer 72 may be resilient and may have engagement portions 179 a and 179 b on their free ends (e.g., hooks or clips) for securely engaging the bottom and side surfaces of cam follower 68.

As best seen in FIG. 20, cannula transfer 74 comprises a sleeve disposed about inner cannula 76. Cannula transfer 74 comprises a proximal end 128, middle section 127, and distal end 126. Upwardly extending members 180 a and 180 b of cam transfer 72 define fork-shaped structures that receive and cradle middle section 127 of cannula transfer 74. Distal end 126 and proximal end 128 of cannula transfer 74 are disposed outwardly of upwardly extending members 180 a and 180 b and are shaped to prevent relative translation between cam transfer 72 and cannula transfer 74. In the depicted embodiments, distal end 126 and proximal end 128 of cannula transfer 74 are enlarged relative to middle section 127 to abut the upwardly extending, fork-shaped members 182 a and 182 b, thereby preventing relative translation between cam transfer 72 and cannula transfer 74. As a result, when cam transfer 72 reciprocates along the length of handpiece 42, cannula transfer 74 reciprocates as well. Because it is affixed to inner cannula 76, when cannula transfer 74 reciprocates, it causes inner cannula 76 to reciprocate within outer cannula 44.

In one exemplary arrangement, motor 62 is a brushed DC motor and may be operably connected to cam 64 in a number of ways. In the embodiment of FIGS. 2 and 3, motor 62 includes a distally extending shaft 66 that extends into a proximal opening 114 and engages recess 116 defined in cam 64. Shaft 66 may be connected to cam 64 via a threaded connection, adhesive, or other known connection means. In an alternate implementation, depicted in FIG. 15, a separate cam coupler 184 is provided. Cam coupler 184 is seated in proximal opening 114 and has a width greater than the diameter of opening 114. Cam coupler 184 is also connected to motor shaft 66 such that rotation of shaft 66 causes cam coupler 184 to rotate, which in turn causes cam 64 to rotate therewith. One revolution of motor shaft 66 causes cam 64 to rotate by one revolution, which in turn causes inner cannula 76 to reciprocate by one complete stroke, i.e., from the position of FIG. 2 to the position of FIG. 3 and back to the position of FIG. 2.

Cam transfer 72 may be connected to cam follower 68 by mechanical means, adhesive means or other known connection means. In one exemplary embodiment, downwardly extending members 178 a and 178 b mechanically clip onto and removably engage cam follower 68. In another embodiment, cam transfer 72 is adhesively affixed to cam follower 68. In yet another embodiment, both mechanical and adhesive connections are used. The ball bearing (not shown) disposed in cam follower hole 70 traverses cam groove 65 as cam 64 rotates, causing cam follower 72 to reciprocate from the proximal position of FIG. 2 to the distal position of FIG. 3. As a result, cam transfer 72, cannula transfer 74 and inner cannula 76 translate between their respective proximal positions of FIG. 2 and their respective distal positions of FIG. 3 when motor 62 and cam 64 rotate. In certain examples (not separately shown), motor 62 may be connected to a cam follower, and the cam follower may be connected to a cam which is in turn operatively connected to the inner cannula. In accordance with these examples, when the motor rotates, the cam follower rotates and causes the cam to reciprocate, thereby causing the inner cannula to reciprocate.

Motor 62 is preferably selected to have a rotational speed that allows inner cannula 76 to reciprocate from the position of FIG. 2 to the position of FIG. 3 and back to the position of FIG. 2 at a rate of at least about 1,000 reciprocations/minute. Reciprocation rates of at least about 1,200 reciprocations/minute are more preferred, and reciprocation rates of at least about 1,500 reciprocations/minute are even more preferred. Reciprocation rates of less than about 2,500 reciprocations/minute are preferred. Reciprocation rates of less than about 2,000 are more preferred, and reciprocation rates of less than about 1,800 reciprocations/minute are even more preferred. As best seen in FIG. 14, the rates of reciprocation of device 40 allow tissue to be severed into “snippets” 112 which are relatively smaller than “slug” tissue samples obtained by many prior devices. As the reciprocation continues, a continuum of severed tissue snippets 112 is obtained.

As mentioned previously, outer cannula 44 includes an opening 49 for receiving tissue into outer cannula lumen 110. As best seen in FIGS. 8-12, opening 49 is preferably defined by a cutting edge 51 that is configured to sever tissue and a non-cutting edge 53 that is not configured to sever tissue. In certain exemplary implementations, cutting edge 53 has a radial depth “d” that is no greater than about 50% of the outer diameter of outer cannula 44. In one exemplary implementation, cutting edge 51 is beveled in a radially inward direction, non-cutting edge 53 is not beveled, and cutting edge 51 is located immediately distally of non-cutting edge 53. Inner cannula distal end 79 is preferably configured to cut tissue. In one exemplary embodiment, distal end 79 is beveled in a radially inward direction around the circumference of inner cannula 76 to provide a sharp edge. As tissue is received in outer cannula opening 49, it is compressed between inner cannula distal end 79 and outer cannula cutting edge 51, causing the received tissue to be severed from the surrounding tissue.

Tissue cutting device 40 is particularly well suited for use in cutting tough tissues such as spinal and brain tissues. Outer cannula 44 and inner cannula 76 comprise materials that are generally rigid, such as rigid plastics or metal. In one preferred implementation, both cannulae comprise stainless steel, and more preferably, 304SS typically used in medical grade instruments.

As best seen in FIGS. 9-13, to facilitate the cutting of tough tissues, inner cannula 76 includes a hinge 80. Hinge 80 is located between inner cannula body section 81 which is located on the proximal side of hinge 80 and inner cannula cutting section 83 which is located on the distal side of hinge 80. In one exemplary arrangement, hinge 80 is a living hinge. As used herein, the term “living hinge” refers to a thin, flexible hinge that joins two relatively more rigid parts together. In one example, hinge 80 is a living hinge that is integrally formed with inner cannula body section 81 and inner cannula section 83 by removing a portion of the circumference of the inner cannula 76 along a length L (FIG. 11). Hinge 80 allows cutting section 83 to pivot about hinge 80 as inner cannula 76 reciprocates within outer cannula 44. As inner cannula 76 translates in the distal direction, it contacts tissue received in outer cannula opening 49 and encounters progressively increasing resistance from the tissue as the tissue is urged in the distal direction. As the resisting force of the tissue increases, cutting section 83 pivots progressively more until a zero annular clearance is obtained between inner cannula distal end 79 and outer cannula opening 49. The received tissue is severed and aspirated in the proximal direction along inner cannula lumen 110 and received in tissue collector 58. Thus, inner cannula lumen 110 provides an aspiration path from the inner cannula distal end 79 to the inner cannula proximal end 77. Hinge 80 allows a generally zero annular clearance to be obtained between inner cannula distal end 79 and outer cannula opening 49 at cutting section 80 while not affecting the annular clearance between inner cannula body section 81 and outer cannula 44. This configuration maximizes tissue cutting while minimizing frictional losses that would otherwise occur due to the frictional engagement of the outer surface of inner cannula body section 81 and the inner surface of outer cannula 44 if a very small annular clearance between the outer cannula 44 and inner cannula 76 were present.

Outer cannula opening 49 may have a number of shapes. In certain examples, when outer cannula opening 49 is viewed in plan, it has a shape that is generally square, rectangular, trapezoidal, ovular, or in the shape of the letter “D.” In certain other exemplary implementations, outer cannula opening 49 is configured to direct tissue so that it may be compressed as inner cannula 76 translates in the distal direction. In one such implementation, depicted in FIGS. 10 and 12, outer cannula opening 49 has a generally triangular shape when outer cannula opening 49 is viewed in plan. As FIGS. 10 and 12 indicate, when viewed in plan, the width of opening 49 in a direction transverse to the outer cannula longitudinal axis varies longitudinally along the length of outer cannula 44, and preferably narrows from the proximal to distal portions of opening 49. When viewed in side elevation, cutting edge 51 slopes in a radially outward direction moving distally along edge 51. As a result, as a tissue sample is distally urged within outer cannula opening 49 by the action of inner cannula 76, the tissue is increasingly compressed in the direction of the circumference of inner cannula 76 (or in the direction of the “width” of opening 49 when viewed in plan). To ensure complete cutting, inner cannula distal end 79 preferably travels to a position that is distal of outer cannula opening 49 during a tissue cutting operation, i.e., there is an inner cannula overstroke.

As mentioned above, tissue cutting device 40 aspirates tissue samples received in inner cannula lumen 78 to cause the tissue samples to move in the proximal direction along the length of the inner cannula 76. In certain methods of use, device 40 is used to resect tissue without collecting tissue samples for further analysis. In such embodiments, a tissue collector need not be provided. In other embodiments wherein tissue collection is desired, device 40 preferably includes a tissue collector 58 into which aspirated tissue samples are deposited during a tissue cutting procedure. Tissue collector 58 may be located remotely from handpiece 42 and outside the sterile field during a tissue cutting operation as shown in FIG. 21A. However, in an alternative embodiment, as best seen in the examples of FIGS. 1-7, tissue collector 58 is removably connected to handpiece 40. In either embodiment, a fluid collection canister 192 is preferably located between tissue collector 58 and a source of vacuum (such as vacuum generator 153 in FIG. 21A) to protect the vacuum generating apparatus from becoming contaminated or damaged by aspirated fluids. In those embodiments that lack a tissue collector, fluid collection canister 192 may be provided to collect both aspirated fluid and tissue.

Referring to FIGS. 4-7, tissue collector 58 is connected to upper housing 52 proximally of the inner cannula 76 to receive the aspirated tissue samples. Tissue collector 58 is a generally cylindrical, hollow body with an interior volume that is in fluid communication with the inner cannula lumen 78 and a source of vacuum (not shown in FIGS. 4-7). Tissue collector 58 is removably secured to housing connector 96 to allow for the periodic removal of collected tissue samples. Tissue collector 58 is preferably secured to upper housing 52 in a manner that provides a substantially leak-proof vacuum seal to maintain consistent aspiration of severed tissue samples. A vacuum hose fitting 59 is formed on the proximal end of tissue collector 58 and is in fluid communication with the interior of tissue collector 58 and with a vacuum generator, as will be discussed below.

In the embodiment of FIGS. 4-5, housing connector 96 is a generally cylindrical, flange extending proximally from upper housing 52. Upper shell 54 and lower shell 56 of upper housing 52 cooperatively define a cavity into which a seal holder 94 is partially disposed. Seal holder 94 includes a distal annular recess in which a seal 92, such as an o-ring, is disposed. Seal holder 94 also includes a central lumen through which inner cannula 76 is slidably disposed. A proximally projecting portion 95 of seal holder 94 projects away from upper housing 52 in the proximal direction and is received within housing connector 96. As best seen in FIGS. 2 and 3, inner cannula proximal end 77 preferably remains within seal holder 94 as inner cannula 76 reciprocates during operation of tissue cutting device 40. However, proximal end 77 moves within seal holder 94 as inner cannula 76 reciprocates. Seal 92 preferably comprises a resilient material such as an elastomeric material. The sealing engagement of seal 92 and inner cannula 76 prevents air or fluids from leaking between inner cannula 76 and upper housing 52 and aids in maintaining consistent aspiration of samples through the inner cannula lumen 78.

Housing connector 96 includes connecting features 98 and 100 which are configured to engage with corresponding connecting features 102 and 104 on tissue collector 58. In the embodiment of FIGS. 4 and 5, connecting features 98 and 100 are “J” shaped slots formed in housing connector 96, and connecting features 102 and 104 are complementary protrusions formed on tissue collector 58 which engage connecting features 98 and 100, respectively. To connect tissue collector 58 to housing connector 96, protrusions 102 and 104 are aligned with slots 98 and 100, and tissue collector 58 is then inserted into housing connector 96 in the distal direction. Tissue collector 58 is then rotated to fully engage protrusions 102 and 104 with slots 98 and 100. A seal 103 is provided around the circumference of tissue collector 58 to sealingly engage the inner surface of housing connector 96.

An alternate embodiment of tissue collector 58 is depicted in FIGS. 6 and 7. In the embodiment of FIGS. 6 and 7, tissue collector 58 is semi-elliptical in cross-section and includes a hollow interior for receiving samples, as in the embodiment of FIGS. 4 and 5. In the embodiment of FIGS. 6 and 7, a cylindrical flange housing connector 96 is not provided. Instead, upper housing 52 is formed with an engagement recess 108 that engages a complementary clip 106 formed on tissue collector 58. In each of the foregoing embodiments, tissue collector 58 may be provided with a filter (not shown) in its interior for collecting solid tissue samples while allowing liquids and gases (e.g., air) to pass through. Exemplary filters include medical grade mesh filters with a mesh size smaller than that of tissue snippets 112.

In the embodiments of FIGS. 4-7, tissue collector 58 preferably has a longitudinal axis that is not collinear with the longitudinal axes of handpiece 42, motor 62, and cam 64. The longitudinal axis of tissue collector 58 is preferably substantially coaxial with the longitudinal axis of inner cannula 76 to yield an “in-line” filter configuration. Tissue collector 58 and inner cannula 76 are both spaced apart from and substantially parallel to the longitudinal axes of handpiece 42, motor 62, and cam 64. Thus, the cutting axis (i.e., the outer cannula longitudinal axis) and sample aspiration path axis are not coaxial with the longitudinal axis of the handpiece 42. As a result, when device 40 is used to cut tissue, the surgeon's view of the cutting axis is not obstructed by his or her hand. In addition, the surgeon can treat the proximal end of the filter as a “gun sight” and align it with a tissue sample to be cut to thereby align the outer cannula 44 with the tissue sample, providing enhanced ergonomic benefits over previous devices, in particular, previous neurosurgical devices. In the case of a device with a remote tissue collector 58 such as the one depicted in FIGS. 21A and 21B, the user can treat the proximal end of upper housing 52 as a gun sight and align it with a target tissue.

When device 40 is used to cut tissue, outer cannula opening 49 must be aligned with the target tissue of interest to receive it for cutting. The entire device 40 can be rotated about the longitudinal axis of handpiece 42 to place outer cannula opening 49 at the desired location. However, this technique can be awkward and may reduce the surgeon's dexterity. Thus, in an exemplary embodiment, device 40 includes a selectively rotatable outer cannula 44. As best seen in FIGS. 18-20, a rotation dial 60 is provided and is rotatably seated in a cavity defined by upper shell 54 and lower shell 56 of upper housing 52. Rotation dial 60 is configured such that when it is rotated, it causes outer cannula 44 to rotate about its longitudinal axis. Rotation dial 60 is preferably connected to an outer cannula connector portion 88. In the embodiment of FIGS. 18-20, outer cannula connector portion 88 is a sleeve that is integrally formed with rotation dial 60 and which is fixedly secured to outer cannula 44 such as by an adhesive or other known connection means. In the exemplary embodiment of FIG. 20 rotation dial 60 has an outer diameter that is greater than that of sleeve 88.

As mentioned previously, inner cannula 76 includes a hinge 80 to allow inner cannula cutting section 83 to pivot toward outer cannula opening 49 when device 40 is in operation. In order to ensure the correct operation of hinge 80, the circumferential alignment of hinge 80 and outer cannula opening 49 should be maintained. Thus, rotation dial 60 is preferably connected to inner cannula 76 such that when rotation dial 60 is rotated, both outer cannula 47 and inner cannula 76 rotate in a fixed angular orientation with respect to one another by an amount that directly corresponds to the amount by which rotation dial 60 is rotated. Rotation dial 60 may be directly connected to inner cannula 76 or may use an intervening connecting device. However, rotation dial 60 should be configured to allow inner cannula 76 to reciprocate with respect to rotation dial 60. As best seen in FIG. 20, rotation dial inner cannula connector 86 may be provided to connect rotation dial 60 to inner cannula 76. Rotation dial inner cannula connector 86 comprises a proximal sleeve 87 disposed about inner cannula 76 and a distal, radially extending annular flange 90 with an outer diameter greater than that of the sleeve 87. Sleeve 87 and flange 90 may be in the shape of circular cylinders. Alternatively, and as shown in FIGS. 18-19, sleeve 87 and flange 90 may be in the shape of a polygonal cylinder. Sleeve 87 is slidably received within the annular cavity 130 at the distal end 126 of the cannula transfer 74 and keyed to the inner surface of cannula transfer 74 at annular cavity 130 such that sleeve 87 can reciprocate with respect to cannula transfer 74 while causing cannula transfer 74 to rotate with sleeve 87 when rotation dial 60 is rotated. When inner cannula 76 is reciprocated, cannula transfer distal end 126 reciprocates with respect to sleeve 87, thereby variably adjusting gap “G” defined within annular cavity 130 (FIG. 20). Alternatively, cannula transfer distal end 126 may be slidably received in an annular cavity formed in sleeve 87 and may be keyed to the inner surface of the annular cavity so that cannula transfer may reciprocate with respect to sleeve 87 while still rotating with sleeve 87 when dial 60 is rotates.

As best seen in FIG. 20, rotation dial 60 includes a first annular cavity 61 that is sized to receive and engage flange 90 in a close fitting relationship. Rotation dial 60 may be press fit to flange 90. In addition, adhesive connections or mechanical connections may be used. Because rotation dial 60 is directly or indirectly connected to both outer cannula 44 and inner cannula 76, both cannulae rotate in direct correspondence to the rotation of rotation dial 60, thereby allowing the user to adjust the orientation of outer cannula opening 49 and inner cannula hinge 80 in a circumferential direction with respect to handpiece 42. As a result, surgeons need not rotate the entire tissue cutting device 40 to obtain the desired angular orientation.

Rotation dial 60, outer cannula 44, and inner cannula 76 are preferably configured for 360° rotation. In addition, tactile indicators are preferably provided on rotation dial 60 to allow a user to reliably determine the extent to which dial 60 has been rotated from a given starting point. The tactile indication may comprise surface features defined on or in the exterior surface of rotation dial 60. In one exemplary embodiment, depicted in FIGS. 18-20, a plurality of ridges 122 is provided around the circumference of rotation dial 60 to provide tactile indication. The ridges also act as grips and facilitate the surgeon's ability to rotate the dial 60 without transferring unwanted motion to the surgical site.

As mentioned previously, vacuum (sub-atmospheric pressure) is applied to tissue collector 58 to aspirate severed tissue samples through inner cannula 76 in the proximal direction. The application of vacuum to inner cannula 76 via tissue collector vacuum hose fitting 59 will have a propensity to produce a vacuum at proximal end 45 of outer cannula 44 if leakage occurs between inner cannula 76 and the components of upper housing 52. The generation of a vacuum at outer cannula proximal end 45 will in turn cause fluids and/or tissue samples at the distal end of outer cannula 44 to flow into the annular clearance between inner cannula 76 and outer cannula 44 that extends from its proximal end at outer cannula proximal end 45 to its distal end at inner cannula distal end 79. This fluid and/or tissue can result in blockage of the annular clearance and increased friction between the inner cannula 76 and outer cannula 44, resulting in degraded performance. Accordingly, a seal 129 is preferably provided to prevent air artifacts, fluid (water, saline, blood, etc.) flow, and tissue sample flow in the annular clearance between inner cannula 76 and outer cannula 44. The seal 129 is preferably disposed adjacent the proximal end of the annular clearance between inner cannula 76 and outer cannula 44, i.e., proximally adjacent to outer cannula proximal end 45. As shown in FIG. 20, seal 129 is preferably annular and circumscribes inner cannula 76, extending from the outer surface of inner cannula 76 in a radially outward direction as well as longitudinally along a portion of the length of inner cannula 76.

In the embodiment of FIG. 20, rotation dial 60 and sleeve 87 act as a seal housing and include a seal cavity 131 which is an annular cavity disposed immediately adjacent to and distal of first annular cavity 61. Seal cavity 131 is sized to accept seal 129 therein. The seal 129 may be a conventional seal such as a solid, flexible and/or elastomeric o-ring. However, seal 129 is preferably amorphous and comprises a thixotropic material that is a semi-solid. It is further preferred that seal 129 fill the entirety of seal cavity 131 to ensure that cavity 131 is substantially leak free. In the exemplary embodiment of FIG. 20, seal cavity 131 has an outer diameter that is greater than the outer diameter of outer cannula 44. Moreover, the annular thickness of seal cavity 131 is preferably greater than the annular clearance between outer cannula 45 and inner cannula 76 to better ensure complete sealing of the annular clearance.

In one exemplary embodiment, seal 129 is a grease—such as the so-called “high vacuum greases”—that is formulated to withstand vacuum conditions. Suitable high vacuum greases include halogenated polymers. The halogenated polymers are preferably based on cyclic ethers or unsaturated hydrocarbon polymeric precursors. In one exemplary embodiment, a perfluroropolyether (PFPE) grease is used. Examples of such greases include the FOMBLIN® family of greases supplied by Solvay Solexis, Inc. Other examples of such greases include polytetrafluroroethylene greases (“PTFE”) such as TEFLON® greases supplied by DuPont. One suitable high vacuum grease is FOMBLIN® Y VAC3 grease, which is a PFPE grease with a PTFE thickener. The semi-solid seal 129 preferably has a kinematic viscosity at 20° C. of at least about 500 cSt, more preferably at least about 800 cSt, and even more preferably at least about 1200 cSt. Semi-solid seal 129 preferably has a kinematic viscosity at 20° C. of no greater than about 2500 cSt, more preferably no greater than about 2000 cSt, and even more preferably no greater than about 1700 cSt.

The use of a semi-solid seal 129 has several advantages. Because the seal is semi-solid, it will tend to absorb and dampen vibrations transmitted from the reciprocation of the inner cannula, thereby reducing overall vibration of device 40, and in particular, the vibration transmitted to outer cannula 44. The dampening of such vibrations is particularly beneficial because it prevents unwanted vibration of outer cannula 44 which can disturb delicate neurosurgical procedures. Moreover, because it is not a solid seal, seal 129 will experience less heating and wear as it is frictionally engaged by the reciprocating inner cannula 76. In certain embodiments, a portion of seal 129 will adhere to the outer surface of inner cannula 76 as it reciprocates producing a zero slip velocity condition at the inner cannula 76 outer surface which may further reduce frictional heating and degradation of seal 129. Because semi-solid seal 129 produces less frictional resistance to the reciprocation of inner cannula 76 as compared to conventional solid seals such as o-rings, it also decreases the required motor power consumption and can facilitate the use of lower torque and lower cost motors, which in turn facilitates making device 40 disposable.

In one configuration, device 40 is connected to a vacuum source and configured for variable aspiration, i.e., configured to supply variable levels of vacuum to inner cannula lumen 78. As depicted in FIG. 21A, in one exemplary implementation, a tissue cutting system is provided which comprises tissue cutting device 40, a tissue collector 58, a controller 132, a vacuum generator 153, a vacuum actuator 144, a controllable valve 146, a vacuum line 151, and a fluid collection canister 192. As mentioned previously, in FIG. 21A tissue collector 58 is located remotely from handpiece 42 and may be placed far enough from the handpiece 42 to remain outside of the sterile field during a tissue cutting operation. As best seen in FIG. 21B, tissue collector 58 is generally the same as the tissue collector 58 depicted in FIGS. 4-5. Vacuum line 151 a connects the distal end of tissue collector 58 to proximally projecting portion 95 of seal holder 94 on the proximal end of tissue cutting device upper housing 52. In one arrangement, the proximal end of vacuum line 15 la includes a hose fitting 59 b that is integrally formed with a tissue collector coupler 296. Coupler 296 is similar in structure to tissue collector connector 96 (FIGS. 4-5) and is a cylindrical structure with a hollow interior for receiving a portion of tissue collector 58. As best seen in FIG. 21B, tissue collector 58 includes projections 202 and 204 which engage complementary slots 298 and 200 in coupler 296 in the same manner that projections 102 and 104 engage slots 98 and 100 in FIGS. 4-5. At the proximal end of tissue collector 58, hose fitting 59 a engages vacuum line 151 b which in turn is connected to fluid collection canister 192. Fluid collection canister 192 is connected to vacuum generator 153 via vacuum line 151 c. Vacuum generator 153 is connected to controllable valve 146 by way of pressure line 147.

The outlet of tissue collection canister 192 is preferably substantially liquid free and is connected to vacuum generator 153 via vacuum line 151 c. Thus, vacuum generator 153 is in fluid communication with tissue collector 58 and inner cannula lumen 78, thereby generating a vacuum at the proximal end 77 of inner cannula 76 to aspirate severed tissue samples from inner cannula distal end 79 to tissue collector 58. The level of vacuum generated by vacuum generator is preferably variable and selectively controllable by a user. Maximum vacuum levels of at least about 0 in Hg. are preferred, and maximum vacuum levels of at least about 1 in Hg. are more preferred. Maximum vacuum levels of at least about 5 in Hg. are even more preferred, and maximum vacuum levels of at least about 10 in Hg. are still more preferred. Maximum vacuum levels of at least about 20 in. Hg. are yet more preferred, and vacuum levels of at least about 29 in. Hg. are most preferred.

The controllable valve 146 and the vacuum generator 153 provide a means for continuously adjusting and controlling the level of vacuum applied to tissue collector 58 and the proximal end of inner cannula lumen 78. Controllable valve 146 is supplied with a pressurized gas, preferably air, or an inert gas such as nitrogen. In one exemplary embodiment, the pressure applied to controllable valve 146 is about 70 psi.

The system further includes an electrical controller 132 which receives and provides signals to the various components to control or monitor their operations. Controller 132 provides control signals to device 40 via motor drive control line 142 to activate or deactivate motor 62. An aspiration valve control line 150 extends from the controller 132 to the controllable valve 146 which provides pressure to the vacuum generator 153. Signals to the controllable valve 146 through line 150 are used to control the amount of vacuum applied to tissue collector 58.

Controller 132 also receives electrical signals from the various components of the system. For instance, a pressure transducer 148 associated with the aspiration controllable valve 146, sends a signal along line 152 to the controller 132. The signal is representative of the pressure supplied through controllable valve 146 to vacuum generator 153. Thus, the transducer 148 provides immediate feedback to the controller which can in turn provide signals to aspiration controllable valve 146.

The user can adjust the system operating parameters by using panel controls such as a console knob 138 and/or one or more depressible controllers, such as a foot pedal 144. In one embodiment, foot pedal 144 can be used to activate the motor 62 in device 40, causing the inner cannula 76 to reciprocate within the outer cannula 44. In another embodiment, foot pedal 144 can be used to control the vacuum level supplied from vacuum generator 153 to tissue collector 58 and inner cannula lumen 78. In another embodiment, foot pedal 144 can be used both to activate motor 62 and to control the vacuum level supplied from vacuum generator 153 to tissue collector 58. In one arrangement foot pedal 144 is configured to variably increase the level of vacuum applied to tissue collector 58 from a minimum level to a maximum level as foot pedal 144 is depressed from a first position to a second position. In such an arrangement, the first position is one in which foot pedal 144 is not depressed all or is only slightly depressed, and the second position is one in which foot pedal 144 is fully depressed. In another embodiment, knob 138 is used to set a preselected maximum vacuum level applied by vacuum generator 153. Thus, by depressing foot pedal 144 from a first fully open position to a second fully closed position, a plurality (preferably a continuum) of vacuum levels can be supplied to tissue collector 58 with the maximum vacuum level being user adjustable via knob 138.

In one exemplary embodiment, foot pedal 144 includes two switches (not shown) for providing variable vacuum and activating motor 62. In one exemplary embodiment, once foot pedal 144 is partially depressed from an open or undepressed position, motor 62 is activated. In accordance with the embodiment, continued depression of foot pedal 144 activates vacuum generator 153. Foot pedal 144 preferably provides continuous movement between a fully open and a fully depressed position which in turn corresponds to a plurality, and preferably a continuum, of vacuum levels that are supplied to inner cannula lumen 78. Once foot pedal 144 is fully depressed, the vacuum level supplied to inner cannula lumen 78 corresponds to a previously selected maximum vacuum level.

In certain illustrative examples, the user will adjust the level of vacuum to achieve a desired level of “traction” in the tissue surrounding the tissue to be severed. As used here in, the term “traction” refers to the exertion of a pulling force on tissue surrounding the target tissue to be severed. In some instances, traction may be visualizable by the surgeon with the use of a magnification instrument, such as a microscope or an endoscope. The level of vacuum will also determine the amount of unsevered tissue that is drawn into outer cannula opening 49, and therefore, the size of the severed tissue snippets 112 (FIG. 14). Therefore, when fine shaving operations are desired, the vacuum level will be a relatively lower level than if debulking (large scale tissue removal) is performed. Of course, the pre-selected maximum vacuum level will also affect the maximum size of tissue that is drawn into outer cannula opening 49, and therefore, will affect the maximum size of severed tissue samples during any one operation. Also, the vacuum level may be adjusted based on the elasticity, fibrotic content, and hardness/softness of the tissue.

Console 132 may also include indicator lights 136, one of which indicates the activation of cutting and one of which indicates the activation of aspiration. Console 132 may further include an analog display 140 with readouts for “aspiration” and “cutter.” The “aspiration” read out indicates the vacuum level supplied to tissue collector 58 from vacuum generator 153. The “cutter” read out indicates the speed of reciprocation of inner cannula 76. In one embodiment, a speed sensor is mounted in device 40 to determine the speed of reciprocation of inner cannula 76 and the sensor is input to controller 132.

As mentioned previously, when device 40 is used to perform a cutting operation, inner cannula 76 reciprocates within outer cannula opening 49 to sever tissue received within outer cannula opening 49. When a cutting operation is complete, it may be preferred to have inner cannula 76 come to rest at a position that is proximal of the proximal edge 53 of outer cannula opening 49 to ensure that tissue is not trapped between inner cannula distal end 79 and outer cannula cutting edge 51. However, in certain methods of use, tissue cutting device 40 may be used as an aspiration wand without cutting any tissue. In these embodiments, the stop position of the inner cannula distal end 79 within outer cannula opening 49 determines the open area of the outer cannula 44, and therefore, the aspiration levels that can be applied immediately adjacent outer cannula opening 49. Thus, in some preferred embodiments, the inner cannula stop position is user adjustable. Tissue cutting device 40 may be used to aspirate a variety of fluids associated with a neurosurgical procedure, including without limitation blood, saline, cerebrospinal fluid, and lactate ringer's solution. In certain examples, the inner cannula stop position is adjusted to provide a desired degree of aspiration, outer cannula 44 is positioned proximate a target tissue, and vacuum is applied to manipulate the target tissue and draw it into outer cannula opening 49. Outer cannula 44 is then moved to a desired location or orientation, thereby moving the target tissue to the desired location or orientation. Once the target tissue has been satisfactorily manipulated, a cutting operation is initiated. By using device 40 in this manner, target tissues can be drawn away from areas where tissue cutting operations are undesirable, and the cutting can be performed remotely from those areas.

In one exemplary system, an inner cannula position control is provided which controls the rest position of inner cannula 76 when motor 62 is deactivated. Referring to FIG. 24, cam rotational position indicators 176 a and 176 b are mounted on the proximal end of cam 62. In an exemplary embodiment, cam rotational position indicators 176 a and 176 b are magnets having opposite poles. A position sensor 174 is mounted on the inner surface of cam housing 69 and generates a signal indicative of the rotational position of indicators 176 a and 176 b relative to position sensor 174. As mentioned previously, the rotation of cam 62 correlates directly to the position of inner cannula 76 within outer cannula 44. Thus, the rotation of cam 62 can be sensed to indirectly determine the position of inner cannula 76. Accordingly, indicators 176 a/176 b and sensor 174 can be used to determine the position of inner cannula 76 with respect to proximal edge 53 of outer cannula opening 49 (FIGS. 10-12).

Referring to FIG. 22, an embodiment of a system for controlling the operation of tissue cutting device 40 is provided. The system includes a main control unit 158 (“MCU”), which (in the embodiment shown) is configured as a microprocessor-based system. In one implementation, MCU 158 is incorporated in controller 132 (FIG. 21A) and is operable to control the various operations of the tissue cutting device 40. Foot switch 144 is electrically connected to a number of inputs of MCU 158 via an equal number, K, of signal paths 156, wherein K may be any integer. Panel controls, such as knob 138, are electrically connected to a number of inputs of MCU 158 via an equal number, J, of signal paths 145, wherein J may be any integer.

Display unit 140 is electrically connected to a number of outputs of MCU 158 via an equal number, Q, of signal paths 141, wherein Q may be any integer. In one exemplary implementation, depicted in FIG. 21A, display unit 140 is provided on console 134.

As mentioned previously, tissue cutting device 40 includes motor 62 coupled to the inner cannula 76 by an inner cannula drive assembly 63. The motor 62 is electrically connected to motor control unit 160 via a number, M, of signal paths 161 wherein M may be any integer. The motor control unit 160 is, in turn, connected to a number of outputs of MCU 158 via an equal number, N, of signal paths 161. Cam rotational position sensor 174 is electrically connected to a motor shaft position feedback input (SPF) of MCU 158 via signal path 162, and provides a motor stop identification signal thereon as will be more fully described hereinafter. The motor shaft stop identification signal provided by sensor 174 on signal path 162 preferably provides MCU 158 with a motor stop identification signal and may optionally provide a cutter speed signal that is proportional to the motor speed for a geared system or identical to the motor speed for a direct drive system.

Handpiece 40 is further mechanically connected to a vacuum unit 168 (e.g., a combination of controllable valve 146 and vacuum generator 153 in FIG. 21A) via conduit 163, whereby the vacuum unit 168 provides a controllable vacuum level to handpiece 40 for aspirating tissue received in inner cannula lumen 78. Vacuum unit 168 is electrically connected to a vacuum control unit 166 via a number, P, of signal paths 169 wherein P may be any integer. The vacuum control unit 166 is, in turn, connected to a number of outputs of MCU 158 via an equal number, L, of signal paths 167, wherein L may be any integer. A vacuum sensor 164, which may be a temperature compensated solid-state pressure sensor, may be positioned within the conduit 151 and electrically connected to a vacuum feedback (VF) input of MCU 158 via signal path 165. Alternatively, the vacuum sensor 165 may be disposed within hand piece 42 or within the vacuum unit 168 itself.

In operation, the MCU 158 is responsive to a vacuum command signal, preferably provided by a corresponding control mechanism associated with control panel 132, foot pedal 144, or an equivalent control mechanism, to provide one or more corresponding vacuum control signals to vacuum control unit 166 along signal paths 167. The vacuum control unit 166, in turn, is responsive to the one or more vacuum control signals to activate the vacuum unit 168 to thereby provide tissue cutting device 40 with a desired level of vacuum. The actual vacuum level provided to tissue cutting device 40 is sensed by vacuum sensor 164, which provides a corresponding vacuum feedback signal to the vacuum feedback input VF of MCU 158. The MCU 158 is then operable to compare the vacuum feedback signal with the vacuum command signal and correspondingly adjust the one or more vacuum control signals to achieve the desired vacuum level within tissue cutting device 40. Such closed-loop feedback techniques are well known in the control systems art.

In one alternative embodiment, the MCU 158 can be replaced by individual microprocessors controlling the input and output for controlling the operation of the motor 62 and the vacuum unit 168. In this alternative embodiment, the motor control and vacuum control microprocessors can be PIC16CXX Series microcontrollers provided by Microchip, Inc. of Chandler Ariz. The motor control microcontrollers can receive input signals from the motor driver 172 (FIG. 23) and position sensor 174, as well as the foot switch 144 and panel controls 132. Likewise, the vacuum microcontroller can receive input signals from the vacuum sensor 164, the foot switch 144 and panel controls 138. Each microcontroller can provide its own output to its driven component and have its own display, such as an LED display, indicative of its operational status. Moreover, the two units can communicate with each other to ensure clean cutting by proper timing of the cutting and aspiration functions.

Referring now to FIG. 23, one exemplary embodiment of the motor control unit 160 is shown in greater detail. The motor control unit 160 in one embodiment includes a pulse width modulation (PWM) generator circuit 170 having a motor speed input connected to one of the MCU outputs 161 ₁. If motor speed control is provided, the output 161 ₁ can provide a variable voltage signal indicative of a desired motor speed and based upon the position of a throttle, foot pedal, or other actuator. In certain embodiments, an additional input is connected to another one of the MCU outputs 161 ₂. The signal at this output 161 ₂ can be a motor slowdown signal as described below. Alternatively, the output 161 ₂ can constitute a braking signal used in connection with a current feedback motor controller. As a further alternative, the slowdown command may be communicated via the motor speed command itself, rather than through a separate signal 161 ₂. In this instance, the output 161 ₂ may not be required.

In the illustrated embodiment, the PWM is disposed within the motor control unit 160. Alternatively, the PWM can be integrated into the MCU 158, or into the separate motor control microprocessor discussed above. In embodiments that include motor speed control, the motor speed input receives a motor speed signal from MCU 158 indicative of desired operational speed of the motor 62. The slowdown input can receive a speed adjustment signal from the MCU 158 based on an actual motor speed signal provided by a motor sensor associated with the motor 62.

A motor driver circuit 172 is electrically connected to PWM generator circuit 170 via signal path 173 and receives a PWM drive signal therefrom, which is a pulse width modulated signal indicative of desired motor speed. The motor driver circuit 172 provides a motor drive signal (MD) to motor 62 via signal path 175. While the disclosed embodiment contemplates digital control of the motor using the PWM generator circuit 170, alternative embodiments can utilize closed loop feedback analog circuits, particularly where slower cutting speeds are contemplated.

The motor drive signal includes a motor stop input that is connected to another one of the MCU outputs 161 ₁. In accordance with one aspect of the present disclosure, MCU 158 provides a motor stop signal on signal path 161 ₃, based on a motor deactivation command provided by foot switch 144 or panel control 138 and also based on a motor stop identification signal provided by sensor 174, to stop the inner cannula 76 in a desired position, as will be more fully described hereinafter. In certain embodiments, only the motor stop signal is utilized to command the motor to stop at the predetermined position. In these certain embodiments, the motor slowdown signal on path 161 ₂ can be eliminated, or the input on path 161 ₂ can be used for other control signals to the motor control circuit.

As mentioned previously, when tissue cutting device 40 is deactivated, inner cannula 76 may come to rest partially disposed within outer cannula opening 49. Referring to FIGS. 25-27, three different stop positions of inner cannula 76 are shown. FIG. 27 shows that inner cannula 76 can be stopped in a position in which a portion of the tissue T is trapped between the outer cannula opening 49 and the inner cannula distal end 79. Efforts at withdrawing outer cannula 44 from the surgical site may accordingly result in tearing of the tissue portion T′ away from the surrounding tissue base T. Surgeons encountering such trapping would typically be required to re-activate tissue cutting device 40 to release the tissue portion T′ from the surrounding tissue base T. To prevent such tissue trapping from occurring, deactivation of the motor 62 is controlled in such a manner that the inner cannula distal end 79 is positioned remotely from the outer cannula opening 49 when inner cannula 76 stops reciprocating. However, in certain methods of use, device 40 is used as an aspiration wand. In those methods, the stop position of inner cannula distal end 79 may be adjusted to different locations within outer cannula opening 49 in order to adjust the level of aspiration supplied to a region of the anatomy proximate outer cannula opening 49. For example, stop positions may be selected that limit the percent open area of outer cannula opening 49 to 25%, 50%, or 75% of the total area of opening 49.

Referring again to FIGS. 23 and 24, controlled deactivation of the motor 62 will now be described in detail. When it is desired to deactivate tissue cutting device 40, a motor stop command is provided such as via foot switch 144 or a panel control 138. In one embodiment, MCU 158 is responsive to the motor stop command to provide a slowdown signal to the PWM generator via signal path 161 ₂ which slows the action of motor 62. Preferably, the slowdown signal corresponds to a predefined signal level operable to drive the motor 62 at a motor speed below a motor speed threshold level. Since motor 62 is a brushed DC motor, it has a rotational resistance or resistive torque associated therewith as described above. In addition, in some cases friction between the inner cannula 76 and outer cannula 44 will increase the rotational resistance. Due to this combined rotational resistance, operation of the motor 62 will cease very rapidly or nearly instantly if the motor drive signal on signal path 142 is disabled while driving motor 62 below the motor speed threshold. Accordingly, when device 40 is used to cut tissue, alignment of position indicators 176 a or 176 b with sensor 174 preferably corresponds to a position of the tissue cutting device 40 at which there is no danger of trapping tissue between inner cannula distal end 79 and the outer cannula opening 49, and sensor 174 is operable to produce the motor stop identification signal when so aligned with indicator 176 a or 176 b.

In one embodiment, MCU 158 is operable to produce a motor stop signal on signal path 161 ₃ when sensor 174 detects alignment of position indicators 176 a or 176 b therewith after one passage thereby of indicator 176 a or 176 b since producing the slowdown signal on signal path 161 ₂. Allowing one passage of indicator 176 a or 176 b by sensor 174 after issuing the slowdown signal ensures that the rotational speed of motor 62 is at or below the motor speed threshold when subsequently issuing the motor stop command, regardless of the position of indicator 176 a or 176 b relative to sensor 174 when the slowdown command was issued. After one passage of indicator 176 a or 176 b by sensor 174 since issuing the slowdown signal, MCU 158 is responsive to the signal provided by sensor 174 indicative of alignment of indicator 176 a or 176 b therewith, to produce the motor stop signal on signal path 161 ₃. The motor driver 172 is responsive to the motor stop signal to produce a motor disable signal on signal path 175. Due to the inherent rotational resistance, motor 62 is responsive to the motor disable signal to immediately cease operation thereof with indicator 176 a or 176 b substantially aligned with sensor 174, and with the inner cannula 76 accordingly positioned so as not to trap tissue between inner cannula distal end 79 and the outer cannula opening 44.

As mentioned above, in one exemplary embodiment, the inner cannula stop position is user adjustable, such as by adjusting a panel control 138 on console 134. In accordance with the embodiment, it is contemplated that the stopped rotational position of cam 64, and therefore the inner cannula distal end 79, may be instead aligned with a predetermined differential distance between the indicator 176 a/176 b and the sensor 174. The braking characteristics of the inner cannula 76 and motor 62 can be ascertained and the stopping distance determined so that this predetermined differential distance can be calibrated accordingly. However, in a preferred embodiment, when inner cannula 76 comes to rest, the distal end 79 is located proximally of the outer cannula opening 44 by a predetermined distance, as shown in FIG. 26.

A method of using device 40 to perform a tissue cutting procedure will now be described in the context of a neurosurgical procedure involving the cutting of a neurological target tissue. In one example, the target tissue is brain tissue, and in another example the target tissue is spinal tissue, for example, the tissue of an intervertebral disk. In certain exemplary methods, the tissue specimen being cut is a tumor or a lesion.

In accordance with the method, it is first determined whether the cutting operation will be a debulking operation or a fine shaving operation or a cutting operation that is somewhere in between a debulking and fine shaving operation. A surgical access path is then created to the tissue sample of interest. In one embodiment, the surgical path is created and/or the target tissue is accessed using an “open” procedure in which the target tissue is open to the atmosphere (e.g., a full open craniotomy). In another embodiment, the surgical path is created and/or the target tissue is accessed using a “closed” procedure in which the target tissue is sealed from the atmosphere.

At this point, the distal end 79 of inner cannula 76 is located proximally of outer cannula opening 69 due to the use of an inner cannula stop position control of the type described previously. The maximum vacuum level to be applied to device 40 is then set using panel controls 138. Generally, higher vacuum levels will be used for debulking procedures than for fine shaving procedures as higher vacuum levels will tend to draw relatively larger sections of tissue into outer cannula opening 49. In one embodiment, the panel control 138 is a knob on console 134 that is rotated to set the desired maximum vacuum level.

In one arrangement, device 40 is configured to be gripped with a single hand during a tissue cutting procedure. Thus, the surgeon will grasp handpiece 42 in the fingers of one hand and insert outer cannula 44 to a location proximate the target tissue. Depending on the hand and the surgeon's orientation with respect to the target tissue, the surgeon may then rotate dial 60 to rotate outer cannula 44 about its own longitudinal axis and orient outer cannula opening 49 immediately adjacent the target tissue. The rotation of outer cannula 44 with dial 60 causes inner cannula 76 to rotate such that a fixed rotational or angular relationship is maintained between inner cannula 76 and outer cannula 44. Once the opening is in the desired orientation, the motor 62 is activated, for example, by beginning to depress pedal 144 from its fully undepressed (open) position to a second partially depressed position which causes motor control unit 160 to send a signal to motor 62 on signal path 142. Motor 62 may also be activated by a panel control 138. The rotation of motor 62 causes cam 64 to rotate, resulting in the reciprocation of cam follower 68 and cam transfer 72. The reciprocation of cam transfer 72 causes cannula transfer 74 to reciprocate, thereby reciprocating inner cannula 76 within outer cannula lumen 110.

Once motor 62 is activated, vacuum is supplied to inner cannula lumen 78. In one embodiment, as the pedal 144 is further depressed (beyond the position at which motor 62 is activated), vacuum generator 153 is activated. The surgeon then adjusts the degree of depression of the foot pedal 144 to obtain the desired level of vacuum by visualizing the movement of the target tissue relative to the outer cannula opening 49. In certain embodiments, the surgeon controls the vacuum level to obtain a desired amount of traction in the tissue surrounding the target tissue. If the surgeon desires to apply the previously set maximum vacuum level, he or she depresses pedal 144 to its fully depressed position.

If desired, the surgeon may depress and partially release the pedal 144 a number of times to manipulate the target tissue in a satisfactory manner. Vacuum controller 166 is manipulable to adjust the setpoint of vacuum generator 153 which is manipulable to adjust the inner cannula vacuum level along a continuum of levels below the pre-selected maximum level. In one embodiment, the extent of depression of foot pedal 144 dictates the vacuum set point supplied to vacuum control unit 166 on signal path 167, and therefore, the amount of vacuum provided by vacuum unit 168. Vacuum sensor 164 measures the vacuum supplied to tissue collector 58 and feeds a signal back to main control unit 158 on signal path 165. The measured vacuum is then compared to the set point applied to vacuum control unit 166 via foot pedal 144, and the signal transmitted to vacuum generator 153 is then adjusted to move the measured vacuum value towards the set point. To obtain a vacuum level equal to the maximum pre-set level, pedal 144 is completely depressed. Maximum vacuum levels of at least about 0 in Hg. are preferred, and maximum vacuum levels of at least about 1 in Hg. are more preferred. Maximum vacuum levels of at least about 5 in Hg. are even more preferred, and maximum vacuum levels of at least about 10 in Hg. are still more preferred. Maximum vacuum levels of at least about 20 in. Hg. are yet more preferred, and vacuum levels of at least about 29 in. Hg. are most preferred.

Due to the resistance of the tissue drawn into outer cannula opening 49, cutting section 83 pivots about hinge 80 and toward outer cannula opening 49 as inner cannula 76 travels in the distal direction. The inner cannula cutting section 83 continues to pivot as it travels in the distal direction, eventually compressing tissue within outer cannula opening 49 and severing it. The severed tissue forms a continuum of tissue snippets 112 (FIG. 14) within inner cannula lumen 78. Due to the vacuum applied to tissue collector 58, snippets 112 are aspirated through inner cannula lumen 78 in the proximal direction. They eventually exit inner cannula lumen 78 at inner cannula proximal end 77 and enter tissue collector 58 (or fluid collection canister 192 if no collector 58 is provided). Any fluids that are aspirated exit tissue collector 58 and are trapped in fluid collection canister 192. The surgeon preferably severs tissue at a cutting rate of at least about 1,000 cuts/minute. Cutting rates of at least about 1,200 cuts/minute are more preferred, and cutting rates of at least about 1,500 cuts/minute are even more preferred. Cutting rates of less than about 2,500 cuts/minute are preferred. Cutting rates of less than about 2,000 are more preferred, and cutting rates of less than about 1,800 cuts/minute are even more preferred.

The surgeon may move device 40 around the target tissue until the desired degree of cutting has been completed. Motor 62 is then deactivated, for example, by completely releasing pedal 144 so it returns to its fully undepressed (open) position. If an inner cannula stop position control is provided, inner cannula 76 preferably comes to rest proximally of outer cannula opening 49, as shown in FIG. 26. Outer cannula 44 is then removed from the surgical site. Tissue collector 58 is then removed from upper housing 52 of handpiece 42, and the collected tissue samples are either discarded or saved for subsequent analysis. Fluids collected in canister 192 are preferably discarded. If the remote tissue collector of FIG. 21A is used, tissue samples may be removed from it without removing outer cannula 44 from the surgical site or otherwise disturbing the surrounding tissue.

It will be appreciated that the tissue cutting devices and methods described herein have broad applications. The foregoing embodiments were chosen and described in order to illustrate principles of the methods and apparatuses as well as some practical applications. The preceding description enables others skilled in the art to utilize methods and apparatuses in various embodiments and with various modifications as are suited to the particular use contemplated. In accordance with the provisions of the patent statutes, the principles and modes of operation of this invention have been explained and illustrated in exemplary embodiments.

It is intended that the scope of the present methods and apparatuses be defined by the following claims. However, it must be understood that this invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. It should be understood by those skilled in the art that various alternatives to the embodiments described herein may be employed in practicing the claims without departing from the spirit and scope as defined in the following claims. The scope of the invention should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems and methods will be incorporated into such future examples. Furthermore, all terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. In sum, it should be understood that the invention is capable of modification and variation and is limited only by the following claims. 

What is claimed as new and desired to be protected by Letters Patent of the United States is:
 1. A tissue removal device, comprising: a handpiece having a housing with a first central longitudinal axis; an outer cannula having an outer cannula lumen, a proximal end, a distal end, and an outer cannula opening adjacent the distal end, wherein the opening defines a cutting edge for severing tissue; an inner cannula disposed in the outer cannula lumen and reciprocable within the outer cannula lumen, the inner cannula having an inner cannula lumen, a proximal end, an open distal end, a cutting edge at the distal end; a motor positioned along the first central longitudinal axis, wherein the motor is connected to a cam that is operatively connected to the inner cannula, such that rotation of the motor causes the cam to rotate; wherein the cam has a continuous groove defined in an outer surface thereof and a proximal opening that is in communication with a proximal recess, wherein the groove has at least one pair of apexes, wherein the members of the at least one pair of apexes are spaced apart from one another along the length of the groove and wherein the proximal opening is configured to receive a motor shaft; and a tissue collector in fluid communication with the inner cannula lumen; wherein rotation of the motor causes the inner cannula to reciprocate within the outer cannula lumen along a second longitudinal axis that is axially offset from the first central longitudinal axis.
 2. The tissue removal device of claim 1, wherein the outer cannula opening has a width that varies longitudinally along the outer cannula and received tissue is compressed between the outer cannula cutting edge and the inner cannula cutting edge.
 3. The tissue removal device of claim 1, wherein when the outer cannula opening is viewed in plan, the outer cannula opening is generally in the shape of a square.
 4. The tissue removal device of claim 1, wherein when the outer cannula opening is viewed in plan, the outer cannula opening is generally in the shape of a trapezoid.
 5. The tissue removal device of claim 1, wherein when the outer cannula opening is viewed in plan, the outer cannula opening is generally in the shape of the letter “D.”
 6. The tissue removal device of claim 1, wherein the motor is operatively connected to a cam follower, wherein the cam follower is connected to the cam, and rotation of the motor causes the cam follower to reciprocate.
 7. The tissue removal device of claim 1, wherein the motor has a rotating shaft that is arranged substantially parallel to the inner cannula and axially spaced apart from the inner cannula along the second longitudinal axis.
 8. The tissue removal device of claim 1, further comprising a linear tissue aspiration path that extends from the inner cannula distal end to the inner cannula proximal end.
 9. The tissue removal device of claim 1, further comprising a vacuum generator in fluid communication with the inner cannula lumen.
 10. The tissue removal device of claim 1, wherein the outer cannula is rotatable with respect to the handpiece, and when the outer cannula is rotated with respect to the handpiece, the inner cannula rotates with respect to the handpiece to maintain a fixed circumferential orientation between the outer cannula and the inner cannula.
 11. The tissue device of claim 1, wherein the tissue collector has a longitudinal axis, the inner cannula has a longitudinal axis, and the tissue collector longitudinal axis is substantially collinear with the inner cannula longitudinal axis.
 12. The tissue removal system of claim 1, wherein the inner cannula reciprocates between a proximal position and a distal position at a rate that is at least about 1000 reciprocations per minute for forming a continuum of severed tissue delivered to the tissue collector.
 13. A method of performing a neurosurgical procedure, comprising: providing a tissue removal device comprising: a handpiece having a housing positioned along a first central longitudinal axis, an outer cannula having an outer cannula lumen, a proximal end, a distal end, and an outer cannula opening adjacent the distal end, wherein the opening defines a cutting edge for severing tissue, and an inner cannula disposed in the outer cannula lumen and reciprocable within the outer cannula lumen, the inner cannula having an inner cannula lumen, a proximal end, an open distal end, a cutting edge at the distal end, a motor positioned along the first central longitudinal axis, wherein the motor is connected to a cam that is operatively connected to the inner cannula, such that rotation of the motor causes cam to rotate; wherein the cam has a continuous groove defined in an outer surface thereof and a proximal opening that is in communication with a proximal recess wherein the groove has at least one pair of apexes, wherein the at least one pair of apexes are spaced apart from one another along the length of the groove and wherein the proximal opening is configured to receive a motor shaft; and a tissue collector in fluid communication with the inner cannula lumen; and activating the motor along the first central longitudinal axis, thereby reciprocating the cam so as to reciprocate the inner cannula within the outer cannula lumen along a second longitudinal axis that is axially offset from the first longitudinal axis, wherein the inner cannula reciprocates between a proximal position and a distal position, such that when the inner cannula is in the proximal position, the target tissue is received in the outer cannula opening, and when the inner cannula is in the distal position, a cutting section of the inner cannula pivots and the received target tissue is severed from surrounding tissue, wherein during the reciprocating step the inner cannula severs tissue at a rate that is at least about 1000 cuts per minute and forms a continuum of severed tissue that is delivered out of the proximal end of the inner cannula directly into the tissue collector.
 14. The method of claim 13, further comprising aspirating the severed tissue in the proximal direction along the inner cannula lumen.
 15. The method of claim 13, further comprising rotating the outer cannula with respect to the handpiece to align the outer cannula opening with the target tissue.
 16. The method of claim 15, wherein the step of rotating the outer cannula with respect to the handpiece further comprises simultaneously rotating the inner cannula with respect to the handpiece to maintain a fixed circumferential orientation between the inner cannula and the outer cannula.
 17. The method of claim 13, wherein the target tissue is spinal tissue.
 18. The method of claim 13, wherein the target tissue is brain tissue.
 19. The method of claim 13, further comprising creating an opening in the patient's anatomy, wherein the step of inserting the outer cannula into the patient proximate the target tissue comprises inserting the outer cannula into the opening.
 20. The method of claim 13, wherein the target tissue comprises a tumor.
 21. The method of claim 13, wherein the target tissue comprises a lesion.
 22. The method of claim 13, wherein the method is an open surgical procedure.
 23. A tissue removal system, comprising: a tissue removal device comprising: a handpiece having a first portion and a second portion, wherein the first portion extends along a first longitudinal axis and the second portion extends along a second longitudinal axis such that the first portion is axially offset from the second portion, an outer cannula having an outer cannula lumen, a proximal end, a distal end, and an outer cannula opening adjacent the distal end, wherein the opening defines a cutting edge for severing tissue and wherein the proximal end of the outer cannula is positioned in the first portion of the housing and is collinear with the first longitudinal axis, an inner cannula disposed in the outer cannula lumen and reciprocable within the outer cannula lumen along the first longitudinal axis, the inner cannula having an inner cannula lumen, a proximal end, an open distal end, a cutting edge at the distal end, a motor positioned in the second portion and disposed along the second longitudinal axis, the motor having a motor shaft; a cam that is operatively connected to the inner cannula and the motor, wherein the cam has a continuous groove defined in an outer surface thereof an a proximal opening that is in communication with a proximal recess, wherein the groove has at least one pair of apexes, wherein the at least pair of apexes are spaced apart from one another along the length of the groove and wherein the proximal opening is configured to receive the motor shaft and a tissue collector in fluid communication with the inner cannula lumen; and a vacuum generator in fluid communication with the inner cannula lumen, wherein the vacuum generator is operable to maintain the inner cannula lumen at a plurality of different vacuum levels for fine shaving and debulking.
 24. The tissue removal system of claim 23, wherein the vacuum generator is operable to maintain the inner cannula lumen at vacuum level that is no greater than a preselected maximum vacuum level while allowing the vacuum level to be variably operated at less than the preselected vacuum level.
 25. The tissue removal system of claim 24, further comprising a vacuum controller operatively connected to the vacuum generator, wherein the vacuum controller is manipulatable to adjust the inner cannula vacuum level along a continuum of vacuum levels that are less than the preselected maximum vacuum level.
 26. The tissue removal system of claim 25, wherein the vacuum controller comprises a foot pedal.
 27. The tissue removal system of claim 26, wherein the foot pedal is depressible from a first position to a second position, and when the foot pedal is depressed to the second position, the inner cannula vacuum level is the preselected maximum vacuum level.
 28. The tissue removal system of claim 23, further comprising a linear tissue sample aspiration path extending from the inner cannula distal end to the inner cannula proximal end, whereby the inner cannula proximal end exits first portion of the housing.
 29. The tissue removal system of claim 23, wherein the tissue collector is disposed between the inner cannula lumen and the vacuum generator.
 30. A tissue removal system, comprising: a handpiece having a first housing portion and a second housing portion, wherein the first housing portion is positioned along a first longitudinal axis and wherein the second housing portion is positioned along a second longitudinal axis such that the second housing portion is axially offset from the first housing portion; an outer cannula positioned collinear with the first longitudinal axis and having an outer cannula lumen, a proximal end, a distal end, and an outer cannula opening adjacent the distal end, wherein the opening defines a cutting edge for severing tissue; an inner cannula disposed in the outer cannula lumen and reciprocable within the outer cannula lumen, the inner cannula having an inner cannula lumen, a proximal end, an open distal end, a cutting edge at the distal end, a living hinge, a cutting section, and a body section, with the hinge being located between the cutting section and the body section, wherein the cutting section is pivotable when the inner cannula reciprocates within the outer cannula lumen; a tissue collector in fluid communication with the inner cannula lumen; a motor positioned in the second housing portion and disposed along the second longitudinal axis, the motor having a motor shaft; a cam that is operatively connected to the motor and to the inner cannula, such that rotation of the motor causes the cam to rotate; wherein the cam has a continuous groove defined in an outer surface thereof and a proximal opening that is in communication with a proximal recess, wherein the groove has at least one pair of apexes, wherein the at least one pair of apexes are spaced apart from one another along the length of the groove and wherein the proximal opening is configured to receive the motor shaft; and a vacuum generator in fluid communication with the inner cannula lumen, wherein the vacuum generator is operable to maintain the inner cannula lumen at a plurality of different vacuum levels for fine shaving and debulking, wherein the inner cannula reciprocates within the outer cannula lumen between a proximal position and a distal position in response to rotation of the motor and at a rate that is no less than about 1000 reciprocations per minute for forming a continuum of severed tissue delivered to the tissue collector.
 31. The tissue removal system of claim 30, wherein the outer cannula opening has a width that varies longitudinally along the outer cannula and received tissue is compressed between the outer cannula cutting edge and the inner cannula cutting edge.
 32. The tissue removal system of claim 30, wherein the motor shaft is substantially parallel to the inner cannula and spaced apart from the inner cannula.
 33. The tissue removal system of claim 30, further comprising a tissue aspiration path from the inner cannula distal end to the inner cannula proximal end.
 34. The tissue removal system of claim 30, wherein the outer cannula is rotatable with respect to the handpiece, and when the outer cannula is rotated, the inner cannula rotates to maintain a fixed circumferential orientation between the outer cannula and the inner cannula.
 35. The tissue removal system of claim 30, wherein the tissue collector has a longitudinal axis that is substantially collinear with the longitudinal axis of the inner cannula.
 36. The tissue removal system of claim 30, wherein the handpiece, the inner cannula, and the outer cannula comprise a tissue removal device.
 37. The tissue removal system of claim 30, wherein the vacuum generator is operable to maintain the inner cannula lumen at a vacuum level that is no greater than a preselected maximum vacuum level while allowing the vacuum level to be variably operated at less than the preselected vacuum level.
 38. The tissue removal system of claim 37, further comprising a vacuum controller operatively connected to the vacuum generator, wherein the vacuum controller is manipulatable to adjust the inner cannula vacuum level along a continuum of vacuum levels that are less than the preselected maximum vacuum level.
 39. The tissue removal system of claim 38, wherein the vacuum controller is a foot pedal.
 40. The tissue removal system of claim 39, wherein the foot pedal is depressible from a first position to a second position, and when the footpedal is depressed to the second position, the inner cannula vacuum level is the preselected maximum vacuum level.
 41. The tissue removal system of claim 30, wherein the tissue collector is disposed between the inner cannula lumen and the vacuum generator. 